Field: This invention relates to a dispensing device, in particular, a device where a battery provides the driving force to electrochemically pump oxygen from air into a chamber, and where the pressure increase resulting from the transport of oxygen pushes fluid from a bladder within said chamber through an outlet in a steady, continuous flow until the fluid contents are exhausted.
State of the Art: Richter in U.S. Pat. No. 3,894,538 disclosed a device for dispensing medicines to man or beast. The medicine was contained in a flexible container which became compressed as fluid was electro-osmotically introduced into an adjacent flexible chamber or when gas was electrolytically produced using precious metal electrodes and an unspecified fixed electrolyte. The rate of medicine discharge was to be regulated using a potentiometer.
Maget in U.S. Pat. No. 4,522,698 disclosed electrochemical prime movers. Embodiments of the invention include a device for dispensing pharmaceuticals to a human body over a substantial period of time at a sustained very low rate, where a battery provides the driving force to transport oxygen from air across an ion-exchange membrane. Pressure in a chamber increases as oxygen transports across the membrane; this increase in pressure drives a piston which forces the contained pharmaceutical fluid to flow through an outlet. The invention requires electrodes which are electrically conductive and act as catalysts to convert molecules to ions; titanium-palladium alloy or palladium black are recommended materials. A controller is utilized to control the magnitude and time pattern of current and voltage applied to the membrane as well as to turn current on and off.
Maget in U.S. Pat. No. 4,886,514 disclosed electrochemically-driven drug dispensers. A potential from an external power source drives an electrochemically-active gas such as hydrogen or oxygen to be transported across a membrane from a fixed volume chamber to a chamber which has a variable volume. The volume of the chamber varies by either flexing an expansible diaphragm-type wall or by displacing a sliding wall, said wall being shared by a second variable volume chamber which contains a fluid drug to be administered. As the electrochemically-active gas is transported to the first variable volume chamber, the drug is forced out of the second variable volume chamber through an outlet. Countering the electrochemical transport of gas across the membrane, the gas diffuses in the opposite direction across the membrane in accordance to the pressure gradient and diffusivity properties of the membrane. A controller compensates for the gas diffusion rate and varies the voltage and current to achieve the desired drug delivery rate in a steady or intermittent mode.
Maget et al. in U.S. Pat. No. 4,902,278 disclosed a fluid delivery micropump. The pump utilizes an air-actuated battery in a fixed closed circuit with an electrochemical cell which drives the transport of oxygen in air across a membrane. The transport applies external pressure to a collapsible reservoir filled with fluid; as a result, fluid is expelled from the reservoir through an outlet. The membrane is preferably a Nafion material (a perfluoro sulfonic polymer) which has been coated with platinum black/10% Teflon. Electrodes are preferably titanium screens. To control the current, a resistor is utilized. The device is activated by removing a protective peel tab to expose air inlet ports to the battery cathode. A disadvantage of this type of system is that shelf life of the device is dependent on the integrity of the seals which prevent air leakage to the battery. If the seals are not perfect, the battery will slowly discharge before the desired time of use.
M. Wilson and S. Gottesfeld have described in articles entitled "High Performance Catalyzed Membranes of Ultra-Low Pt Loadings for Polymer Electrolytic Fuel Cells," and "Thin-Film Catalyst Layers for Polymer Electrolyte Fuel Cell Electrodes" published, respectively in, J. Electrochem, Soc. Vol. 139 no. 2, Feb. 1992, 628-630, and Journal of Applied Electrochemistry 22 (1992) 1-7, two methods for applying thin film catalytic electrodes to cationic membranes. In each case, a mixture of Pt and C are utilized as the catalyst and electronic conductors while solubilized Nafion (from duPont) is used as the binder and ionic conductor for the electrodes. The electrodes were designed for and tested in fuel cell applications. While such an electrode is excellent for an oxygen-reducing cathode, it is unsatisfactory for an oxygen evolving anode since current density decays considerably in a short time.
J. Ahn and R. Holze, in "Bifunctional electrodes for an integrated water-electrolysis and hydrogen-oxygen fuel cell with a solid polymer electrolyte," published in J. of Applied Electrochemistry Vol. 22 (1992) pp. 1167-1173, present data where Ru-oxide, Ir/Ru-oxide, Ir-oxide, Ir, Rh-oxide, Rh, Pt and Rh/Ru-oxide were utilized as catalysts for oxygen evolving electrodes. Of these catalysts, Pt was one of the worst catalyst. Ru-oxide, Ir/Ru-oxide, Ir-oxide and Ir were the better catalysts. Ahn and Holze, in their study, mixed these various catalysts powders with 10% PTFE and formed porous layers which were pressed on to Nafion membranes.
K. V. Ramesh, P. R. Sarode, S. Vasudevan, and A. K. Shukla in "preparation and characterization of carbon-based fuel-cell electrodes with platinum-group bimetallic catalysts," J. Electroanal. Chem., 223 (1987) 91-106 present data indicating that 4% Pt+6% Ru dispersed on activated carbon forms an elctrocatalyst/electroconductor which is superior to either Pt or Ru catalysts for the reduction of oxygen in a fuel cell application. Ramesh et. al. also describe a procedure for dispensing the Pt/Ru alloy on activated carbon by reducing a solution of chloroplative acid and ruthenium chloride in the presence of the activated carbon.
Tuck describes in Modern Battery Technology, Ellis Horwood Ltd. (publisher) 1991, pp. 125-160, the hardware components commonly used in vast quantities in the small-battery industry. Utilization of such components for different kinds of devices is unknown.
The prior art includes several devices which are capable of performing the general function of the device presently disclosed. Thermal units, using an electrical resistor as a heat source, are made to dispense fragrances within a room. These units consume considerable power and plug into a typical 110 v house outlet. These units are not portable and do not dispense the volatile fragrances at a constant rate.
Thus, the prior art has not satisfied a demand which exists for a device which 1) has a design which can dispense a fluid over a nearly constant rate for an extended period of time, 2) has a simple design which is conducive to fabrication, 3) has a design which minimizes the use of materials which are not readily available, and 4) which is small in size and portable, i.e. battery powered. The present invention especially offers advantages relating to the last two factors, which until now have precluded the widespread use of the prior art in disposable consumer products.